Research and development on a region extraction technique with which a moving object is detected by extracting a region of the moving object in an image from the image including an image of the moving object (hereinafter referred simply to as “moving object”) have been widely carried out. The technique of extracting the region of a moving object is a basic technique commonly used for: focus control and image quality improvement processing in a digital video camera or a digital still camera; a driving safety support system for vehicles; or a collision avoidance control or an alarm for avoiding collision which are used for a robot to avoid collision against a moving object.
Among techniques for detecting a moving object in an image, a method generally used is learning information on a shape of the moving object in advance; performing matching between the learnt information on a shape and a region in the image while scanning the image; and extracting a region with a high degree of matching as an object to be detected, as described in Non Patent Literature 1, for example.
In addition, Non Patent Literatures 2 to 5 disclose a method of tracking a moving object in a crowded scene in which occlusion is likely to occur, Unlike Non Patent Literature 1, these methods extract trajectories from video without using the information on a shape, and perform clustering on each of the trajectories based on the similarity of the trajectories, thereby allowing extracting, as classes, moving objects each having a different motion and tracking the extracted moving objects. It is effective, in particular, for tracking of an occluded object which is difficult to be extracted with the moving object extracting method in which information on a shape is used.